Preparation method of tetrazole

Abstract

The invention discloses a tetrazole preparation method, which comprises: S1, carrying out a reflux reaction on benzyl chloride and sodium thiocyanate in a first solvent, filtering, and carrying out atmospheric distillation to obtain benzyl thiocyanate; s2, dissolving benzyl thiocyanate and sodium azide in a second solvent, then adding ammonium chloride to carry out reflux cyclization reaction, adjusting H to 2-3 by using hydrochloric acid after the reaction is finished, cooling to 0 DEG C, and separating out 5-benzyl thio-1H-tetrazole; and S3, carrying out hydrogenation and reflux benzyl sulfenyl removal reaction on the 5-benzyl sulfenyl-1H-tetrazole prepared in the step S2 in a third solvent in a high-pressure kettle by taking Raney Ni as a catalyst, so as to obtain tetrazole. The preparation method comprises the following steps: preparing benzyl thiocyanate by taking benzyl chloride and sodium thiocyanate as raw materials; the preparation method comprises the following steps: carrying out ring closing on benzyl thiocyanate and sodium azide to synthesize 5-benzyl thio-1H-tetrazole; and pressurizing the 2, 5-benzyl sulfenyl-1H-tetrazole, and removing benzyl sulfenyl to obtain the product. The method has the advantages of yield of 54%, simple operation, small environmental pollution and low cost, and is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, in particular to a method for preparing tetrazole. Background Art

[0002] Tetrazol is an important chemical intermediate. The introduction of different substituents can generate a series of tetrazole compounds, which are used in medicine, pesticides, daily chemicals and other fields.

[0003] There are generally two methods for the synthesis of tetrazole:

[0004] Method 1: The product is obtained by reacting hydrazoic acid with hydrocyanic acid under high pressure and in a closed environment. Since both hydrazoic acid and hydrocyanic acid are highly toxic substances and the high-pressure reaction is very dangerous, this method is not suitable for industrial production.

[0005]

[0006] Method 2: It is prepared by diazotization degradation of aminotetrazolyl with nitrous acid. Diazotization is dangerous and easily explodes, and the yield is low.

[0007]

[0008] The object of the present invention is to provide a new process for synthesizing tetrazole to overcome the above technical problems. Summary of the invention

[0009] Based on the technical problems existing in the background technology, the present invention proposes a method for preparing tetrazole, wherein benzyl thiocyanate is prepared from benzyl chloride and sodium thiocyanate as raw materials; benzyl thiocyanate and sodium azide are cyclized to synthesize 5-benzylthio-1H-tetrazole; 5-benzylthio-1H-tetrazole is pressurized and debenzylthioated to obtain the product. The method has a yield of 54%, is simple to operate, has little environmental pollution, is low in cost, and is suitable for industrial production.

[0010] The preparation method of tetrazole proposed by the present invention comprises the following steps:

[0011] S1: Preparation of benzyl thiocyanate;

[0012] S2: Preparation of 5-benzylthio-1H-tetrazolyl;

[0013] S3: Preparation of tetrazole

[0014] The 5-benzylthio-1H-tetrazole prepared in S2 is subjected to hydrogenation and reflux debenzylation reaction in a third solvent using RaneyNi as a catalyst in an autoclave to obtain tetrazole.

[0015] Preferably, the third solvent in S3 is one or more of water, methanol, ethanol and acetonitrile.

[0016] Preferably, the amount of Raney Ni added in S3 is 10-30% of the amount of 5-benzylthio-1H-tetrazolyl substance.

[0017] Preferably, the reaction temperature in S3 is not less than 55° C., and the reaction pressure is 0.2-0.6 MPa.

[0018] Preferably, the preparation method of benzyl thiocyanate in S1 comprises the following steps: reflux reaction of benzyl chloride and sodium thiocyanate in a first solvent, filtering and distilling at normal pressure to obtain benzyl thiocyanate.

[0019] Preferably, the first solvent is one or more of anhydrous ethanol, 95% ethanol, methanol, isopropanol, acetonitrile, benzene, toluene and xylene.

[0020] Preferably, the amount of sodium thiocyanate added is 1-1.5 times the amount of benzyl chloride.

[0021] Preferably, the reflux reaction temperature is not less than 55° C., and the reaction time is 4-6 h.

[0022] Preferably, the preparation method of 5-benzenethio-1H-tetrazole in S2 has the following steps: dissolving benzyl thiocyanate and sodium azide in a second solvent, then adding ammonium chloride to carry out a reflux cyclization reaction, adjusting the pH to 2-3 with hydrochloric acid after the reaction, cooling to 0°C, and precipitating 5-benzenethio-1H-tetrazole.

[0023] Preferably, the second solvent is one or more of water, methanol, ethanol and acetonitrile.

[0024] Preferably, the molar ratio of benzyl thiocyanate, sodium azide and ammonium chloride is 1:1-1.4:1-1.5.

[0025] Preferably, the temperature of the reflux cyclization reaction is not less than 60° C., and the reaction time is 4-6 h.

[0026] Preferably, the autoclave comprises a reactor body, a first motor is fixed on the top of the reactor body, a first gear is fixed on the rotating end of the first motor, a connecting pipe is movably connected to the top of the reactor body, a second gear meshing with the first gear is fixed on the surface of the connecting pipe, and a support rod is fixed on the bottom of the connecting pipe;

[0027] A bidirectional synchronous motor is fixed inside the support rod, a lead screw is fixed to the left and right rotating ends of the bidirectional synchronous motor, a moving groove is opened on the top of the support rod, a moving block threadedly connected to the lead screw is installed inside the moving groove, a connecting rod is fixed at the bottom of the moving block, and a scraping blade is fixed on the outer surface of the connecting rod;

[0028] A water pump is fixed on the top of the reactor body, a water tank is fixed on one end of the water pump, and the other end of the water pump is fixed to the top of the reactor body. A delivery pipe is fixed on the surface of the connecting pipe, and the other end of the delivery pipe is fixed to the connecting rod. A plurality of spray ports are opened on the surface of the connecting rod;

[0029] Preferably, a slide groove is provided on the inner wall of the movable groove, and a sliding block fixed to the movable block is movable inside the slide groove;

[0030] Preferably, a stirring rod is fixed at the bottom of the support rod, and a plurality of stirring blades are fixed in an array on the outer surface of the stirring rod;

[0031] Preferably, a feed pipe is fixed on the top of the reactor body, and a discharge pipe is fixed on the bottom of the reactor body;

[0032] Preferably, a support block is fixed on the outer surface of the reactor body, and a plurality of support legs are fixed on the bottom of the support block;

[0033] Preferably, the water tank, water pump, connecting pipe, delivery pipe and connecting rod are interconnected.

[0034] Beneficial technical effects of the present invention:

[0035] (1) The present invention uses benzyl chloride and sodium thiocyanate as raw materials to prepare benzyl thiocyanate; benzyl thiocyanate and sodium azide are cyclized to synthesize 5-benzylthio-1H-tetrazolyl; 5-benzylthio-1H-tetrazolyl is pressurized and debenzylthioated to obtain the product. The method has a yield of 54%, is simple to operate, has little environmental pollution, is low in cost, and is suitable for industrial production.

[0036] (2) The present invention drives the scraper blade to move inward or outward through a bidirectional synchronous motor, a screw rod, a moving block and a connecting rod. When the interior of the reactor body needs to be stirred, the connecting rod and the scraper blade can stir the raw materials inside the reactor body. When the raw materials remaining on the interior of the reactor body need to be removed, the scraper blade is moved to contact the inner wall of the reactor body. At this time, the water pump is started to transport the cleaning liquid in the water tank to the interior of the connecting rod through the connecting pipe and the conveying pipe, and then the interior of the reactor body is sprayed through the spray port opened on the surface of the connecting rod. At this time, the raw materials adsorbed on the inner wall of the reactor body are cleaned and scraped by rotating the connecting rod and the scraper blade, so that the scraper blade is away from the inner wall of the reactor body during the stirring process, thereby reducing the wear of the inner wall of the reactor body and the scraper blade, increasing the service life of the inner wall of the reactor body and the scraper blade, and also facilitating the cleaning of the interior of the reactor body. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the three-dimensional structure of the autoclave proposed by the present invention;

[0038] Figure 2 This is a schematic diagram of the internal structure of the reactor body of the autoclave proposed by the present invention;

[0039] Figure 3 This is a schematic diagram of the structure of the conveying assembly of the autoclave proposed by the present invention;

[0040] Figure 4 This is a schematic diagram of the structure of the stirring assembly of the autoclave proposed by the present invention;

[0041] Figure 5 This is a schematic diagram of the structure of the rotating assembly of the autoclave proposed by the present invention;

[0042] Figure 6 This is a schematic diagram of the structure of the moving components of the autoclave proposed by the present invention. DETAILED DESCRIPTION

[0043] The present invention will be further explained below in conjunction with specific embodiments.

[0044] Reference Figure 1-6 The autoclave proposed by the present invention comprises a reactor body 1, a first motor 2 is fixed on the top of the reactor body 1, a first gear 18 is fixed on the rotating end of the first motor, a bearing is fixed inside the top side of the reactor body 1, and a connecting pipe 19 is fixed on the rotating part inside the bearing, so that the connecting pipe 19 can be limited and rotated at the same time, a second gear 20 meshing with the first gear 18 is fixed on the surface of the connecting pipe 19, a supporting rod is fixed on the bottom of the connecting pipe 19, and the second gear 20, the connecting pipe 19 and 3 are driven to rotate by the rotation of the first gear 18, a bidirectional synchronous motor 4 is fixed inside the supporting rod 3, and a screw rod is fixed on the left and right rotating ends of the bidirectional synchronous motor 4 5. The screw rods 5 at both ends are driven to rotate by the bidirectional synchronous motor 4 at the same time. A moving groove 6 is provided on the top of the support rod 3. The moving block 7 is limited by the moving groove 6. The moving block 7 is installed inside the moving groove 6 and is threadedly connected to the screw rod 5. The moving block 7 is driven to move inward or outward by the rotation of the screw rod 5. A connecting rod 8 is fixed to the bottom of the moving block 7. A scraping blade 9 is fixed to the outer surface of the connecting rod 8. The inside of the reactor body 1 is scraped by the scraping blade 9. A sliding groove 10 is provided on the inner wall of the moving groove 6. A sliding block 11 fixed to the moving block 7 is movable inside the sliding groove 10. The movement of the moving block 7 is limited by the sliding groove 10 and the sliding block 11.

[0045] Reference Figure 1-2A stirring rod 12 is fixed to the bottom of the support rod 3, and a plurality of stirring blades 13 are fixed in an array on the outer surface of the stirring rod 12, and the interior of the reactor body 1 is stirred by the stirring blades 13. A feeding pipe 14 is fixed to the top of the reactor body 1, and a discharging pipe 15 is fixed to the bottom of the reactor body 1. A supporting block 16 is fixed to the outer surface of the reactor body 1, and a plurality of supporting legs 17 are fixed to the bottom of the supporting block 16, and the entire device is supported by the supporting legs 17.

[0046] Reference Figure 3 A water pump 22 is fixed on the top of the reactor body 1, a water tank 21 is fixed to one end of the water pump 22, and the other end of the water pump 22 is fixed to the top of the reactor body 1. A delivery pipe 23 is fixed to the surface of the connecting pipe 19, and the other end of the delivery pipe 23 is fixed to the connecting rod 8. The cleaning liquid inside the water tank 21 is delivered to the inside of the connecting rod 8 by the water pump 22. Several spraying ports are opened on the surface of the connecting rod 8. The water tank 21, the water pump 22, the connecting pipe 19, the delivery pipe 23 and the connecting rod 8 are interconnected, so that the cleaning liquid inside the water tank 21 can be sprayed onto the inner wall of the reactor body 1 through the spraying ports.

[0047] When the device is in use, the raw materials to be processed are poured into the interior of the reactor body 1 through the feed pipe 14. At this time, the first motor 2 is started to rotate the support rod 3 fixed to its rotating end. The rotation of the support rod 3 drives the stirring rod 12 and the stirring blade 13 to rotate, and at the same time drives the connecting rod 8 and the scraping blade 9 to rotate. The raw materials inside the reactor body 1 are stirred by the stirring blade 13, the connecting rod 8 and the scraping blade 9. The raw materials after stirring are discharged through the discharge pipe 15. When the inner wall of the reactor body 1 needs to be scraped, the two-way synchronous motor 4 is started to drive the screw rod 5 to rotate. The rotation of the screw rod 5 drives the moving block 7 to move in the relative direction, so that the scraping blade 9 and the reactor body are moved relative to each other. The inner wall of the reactor body 1 is contacted, and the water pump 22 is started at this time to transport the cleaning liquid in the water tank 21 to the inside of the connecting rod 8 through the connecting pipe 19 and the delivery pipe 23, and then spray the inside of the reactor body 1 through the spraying port opened on the surface of the connecting rod 8. At this time, the support rod 3 and the scraper blade 9 are driven to rotate by the first motor 2, so that the scraper blade 9 can better clean and scrape the raw materials adsorbed on the inner wall of the reactor body 1, so that the scraper blade 9 only contacts with the inner wall of the reactor body 1 when scraping it, thereby reducing the wear of the inner wall of the reactor body 1 and the scraper blade 9, increasing the service life of the inner wall of the reactor body 1 and the scraper blade 9, and also facilitating the cleaning of the inside of the reactor body 1.

[0048] Example 1

[0049] The preparation method of tetrazole proposed by the present invention has the following steps:

[0050] (1) Preparation of benzyl thiocyanate crystals using benzyl chloride and sodium thiocyanate as raw materials

[0051] 12.65 g (0.1 mol) of benzyl chloride and 9.72 g (0.12 mol) of sodium thiocyanate were refluxed in 120 mL of ethanol as solvent for 5 h. The reaction was terminated when the benzyl chloride completely disappeared. The generated salt was filtered and the solvent ethanol was distilled off under reduced pressure to obtain the product benzyl thiocyanate, a yellow liquid that turned into slightly yellow needle-shaped crystals upon cooling. The yield was 94.1%.

[0052]

[0053] (2) Synthesis of 5-benzylthio-1H-tetrazolyl crystals using benzyl thiocyanate and sodium azide as raw materials

[0054] 11.92g (0.08mol) of benzylic thiocyanate, 6.5g (0.1mol) of sodium azide and 5.35g (0.1mol) of ammonium chloride were refluxed for 6h in 75mL of water and 15mL of ethanol as solvents to complete the reaction. The mixture was cooled to room temperature, the pH value was adjusted to 2 with hydrochloric acid, and the temperature was cooled to 0°C to precipitate white solid 5-benzylic thiocyanate-1H-tetrazolyl with a yield of 75.7%.

[0055]

[0056] (3) Synthesis of tetrazole using 5-benzylthio-1H-tetrazole as raw material

[0057] 9.6 g (0.05 mol) of 5-benzylthio-1H-tetrazole was placed in an autoclave with anhydrous ethanol as solvent and 3 g of RaneyNi, and hydrogen was passed through the autoclave at 0.3 MPa. The product tetrazole was obtained by reflux for desulfurization with a yield of 54.5%.

[0058]

[0059] Example 2

[0060] The preparation method of tetrazole proposed by the present invention has the following steps:

[0061] (1) Preparation of benzyl thiocyanate crystals using benzyl chloride and sodium thiocyanate as raw materials

[0062] 12.65 g (0.1 mol) of benzyl chloride and 8.1 g (0.1 mol) of sodium thiocyanate were refluxed in 100 mL of ethanol as solvent for 5 h. The reaction was terminated when the benzyl chloride completely disappeared. The generated salt was filtered and the solvent ethanol was distilled off under reduced pressure to obtain the product benzyl thiocyanate, a yellow liquid that turned into slightly yellow needle-shaped crystals upon cooling. The yield was 91.3%.

[0063] (2) Synthesis of 5-benzylthio-1H-tetrazolyl crystals using benzyl thiocyanate and sodium azide as raw materials

[0064] 14.9g (0.1mol) of benzylic thiocyanate, 6.5g (0.1mol) of sodium azide and 5.35g (0.1mol) of ammonium chloride were refluxed for 6h in 75mL of water and 15mL of ethanol as solvents to complete the reaction. The mixture was cooled to room temperature, the pH value was adjusted to 2 with hydrochloric acid, and the temperature was cooled to 0°C to precipitate white solid 5-benzylic thiocyanate-1H-tetrazolyl with a yield of 72.8%.

[0065] (3) Synthesis of tetrazole using 5-benzylthio-1H-tetrazole as raw material

[0066] 9.6 g (0.05 mol) of 5-benzylthio-1H-tetrazole was placed in an autoclave with anhydrous ethanol as solvent and 2 g of RaneyNi, and hydrogen was passed through the autoclave at 0.2 MPa. The product tetrazole was obtained by reflux for desulfurization with a yield of 51.6%.

[0067] Example 3

[0068] The preparation method of tetrazole proposed by the present invention has the following steps:

[0069] (1) Preparation of benzyl thiocyanate crystals using benzyl chloride and sodium thiocyanate as raw materials

[0070] 12.65 g (0.1 mol) of benzyl chloride and 12.15 g (0.15 mol) of sodium thiocyanate were refluxed in 150 mL of ethanol as solvent for 6 h. The reaction was terminated when the benzyl chloride completely disappeared. The generated salt was filtered and the solvent ethanol was distilled off under reduced pressure to obtain the product benzyl thiocyanate, a yellow liquid that turned into slightly yellow needle-shaped crystals upon cooling. The yield was 93.2%.

[0071] (2) Synthesis of 5-benzylthio-1H-tetrazolyl crystals using benzyl thiocyanate and sodium azide as raw materials

[0072] 14.9g (0.1mol) of benzylic thiocyanate, 9.1g (0.1mol) of sodium azide and 8.025g (0.1mol) of ammonium chloride were refluxed for 6h in 75mL of water and 15mL of ethanol as solvents to complete the reaction. The mixture was cooled to room temperature, the pH value was adjusted to 2 with hydrochloric acid, and the temperature was cooled to 0°C to precipitate white solid 5-benzylic thiocyanate-1H-tetrazolyl with a yield of 73.5%.

[0073] (3) Synthesis of tetrazole using 5-benzylthio-1H-tetrazole as raw material

[0074] 9.6 g (0.05 mol) of 5-benzylthio-1H-tetrazole was placed in an autoclave with anhydrous ethanol as solvent and 4 g of RaneyNi, and hydrogen was passed through the autoclave at 0.6 MPa. The product tetrazole was obtained by reflux for desulfurization with a yield of 52.9%.

Claims

1. A method for preparing tetrazole, characterized in that: The steps are as follows: S1: Preparation of benzyl thiocyanate; S2: Preparation of 5-benzylthio-1H-tetrazolyl; S3: Preparation of tetrazole The 5-benzylthio-1H-tetrazole prepared in S2 is subjected to hydrogenation and reflux debenzylation reaction in a third solvent using RaneyNi as a catalyst in an autoclave to obtain tetrazole.

2. The method for preparing tetrazole according to claim 1, characterized in that The third solvent in S3 is one or more of water, methanol, ethanol and acetonitrile.

3. The method for preparing tetrazole according to claim 1, characterized in that The amount of Raney Ni added in S3 is 10-30% of the amount of 5-benzylthio-1H-tetrazolyl substance.

4. The method for preparing tetrazole according to claim 1, characterized in that The reaction temperature in S3 is not less than 55°C, and the reaction pressure is 0.2-0.6MPa.

5. The method for preparing tetrazole according to claim 1, characterized in that: The preparation method of benzyl thiocyanate in S1 has the following steps: reflux reaction of benzyl chloride and sodium thiocyanate in a first solvent, filtering and distilling at normal pressure to obtain benzyl thiocyanate.

6. The method for preparing tetrazole according to claim 5, characterized in that: The first solvent is one or more of anhydrous ethanol, 95% ethanol, methanol, isopropanol, acetonitrile, benzene, toluene and xylene.

7. The method for preparing tetrazole according to claim 5, characterized in that: The amount of sodium thiocyanate added is 1-1.5 times the mass of benzyl chloride.

8. The method for preparing tetrazole according to claim 5, characterized in that: The temperature of the reflux reaction is not less than 55°C, and the reaction time is 4-6h.

9. The method for preparing tetrazole according to claim 1, characterized in that: The preparation method of 5-benzylthio-1H-tetrazole in S2 has the following steps: dissolving benzyl thiocyanate and sodium azide in a second solvent, then adding ammonium chloride to carry out a reflux cyclization reaction, adjusting the pH to 2-3 with hydrochloric acid after the reaction, cooling to 0°C, and precipitating 5-benzylthio-1H-tetrazole; Preferably, the second solvent is one or more of water, methanol, ethanol and acetonitrile; Preferably, the molar ratio of benzyl thiocyanate, sodium azide and ammonium chloride is 1:1-1.4:1-1.5; Preferably, the temperature of the reflux cyclization reaction is not less than 60° C., and the reaction time is 4-6 h.

10. The method for preparing tetrazole according to claim 1, characterized in that: The autoclave comprises a reactor body, a first motor is fixed on the top of the reactor body, a first gear is fixed on the rotating end of the first motor, a connecting pipe is movably connected to the top of the reactor body, a second gear meshing with the first gear is fixed on the surface of the connecting pipe, and a supporting rod is fixed on the bottom of the connecting pipe; A bidirectional synchronous motor is fixed inside the support rod, a lead screw is fixed to the left and right rotating ends of the bidirectional synchronous motor, a moving groove is opened on the top of the support rod, a moving block threadedly connected to the lead screw is installed inside the moving groove, a connecting rod is fixed at the bottom of the moving block, and a scraping blade is fixed on the outer surface of the connecting rod; A water pump is fixed on the top of the reactor body, a water tank is fixed on one end of the water pump, and the other end of the water pump is fixed to the top of the reactor body. A delivery pipe is fixed on the surface of the connecting pipe, and the other end of the delivery pipe is fixed to the connecting rod. A plurality of spray ports are opened on the surface of the connecting rod; Preferably, a slide groove is provided on the inner wall of the movable groove, and a sliding block fixed to the movable block is movable inside the slide groove; Preferably, a stirring rod is fixed at the bottom of the support rod, and a plurality of stirring blades are fixed in an array on the outer surface of the stirring rod; Preferably, a feed pipe is fixed on the top of the reactor body, and a discharge pipe is fixed on the bottom of the reactor body; Preferably, a support block is fixed on the outer surface of the reactor body, and a plurality of support legs are fixed on the bottom of the support block; Preferably, the water tank, water pump, connecting pipe, delivery pipe and connecting rod are interconnected.

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